A “unit load device” or a “universal load device”, referred to shortly as “ULD”, is a unit used to load luggage, or freight onto an aircraft. ULDs come in two forms: pallets and containers. ULD pallets are rugged sheets, e.g. made of aluminum, with rims designed to lock onto cargo net lugs. ULD containers, also known as cans and pods, are closed containers, e.g., made of aluminum or combination of aluminum (frame) and polycarbonate resin (walls). Some containers may have built-in refrigeration units, for example. FIG. 1A presents a pallet, while FIG. 1B presents a container. Hereinafter, each ULD, either a container, a pallet or any other type of ULD, constitutes an “air cargo unit”, or shortly, a “unit”.
Air cargo units are loaded onto a cargo area of an aircraft. On their way from the aircraft to a loading station during unloading, or from the loading station to the aircraft during loading, the units are pulled by a tractor. The tractor can pull a number of units at the same time, including several containers, several pallets, or a combination thereof. While pulled by a tractor, the units are mounted on trolleys, e.g., with a single pallet or single or twin containers on each trolley. Using other words, a unit is carryable by a trolley. The tractor carries several such trolleys.
It is appreciated that units differ in size and shape in order to fit into the cargo area of the aircraft. Hence, there are different types of containers and pallets. Each unit has characteristic shape and dimensions.
All ULDs are identified by their “ULD number”, sometimes referred to also as a “ULD identifier”. A three-letter prefix identifies its type, followed by a 4 or 5 digit serial number (4 if prior to Oct. 1, 1993; either 4 or 5 if post Oct. 1, 1993) to uniquely identify it from others of the same type, and ending with a two character (alpha-numerical) suffix identifying the ULD's owner (if an airline, often the same as IATA, the International Air Transport Association designator codes). Generally, the prefix is of the form “UBC”, wherein: U represents the ULD category (such as container or pallet); B represents the base dimensions (Latin letter); and C stands for Contour/Compatibility (Latin letter).
For example:                In “DQF0631R7” illustrated in FIG. 2A, the ULD number indicates that the unit is a container (U=′D′).        In “PMC 22106 MP”, illustrated in FIG. 2B, U=′P,′ indicating that the unit is a certified aircraft pallet, B=′M′ (96″×125″), C=′C′. The unique number is 22106, and its owner is Martinair, represented by “MP”.        
The necessity of monitoring and locating airborne cargo has been identified and dealt with before. For example, U.S. Pat. No. 7,198,227 (“Aircraft Cargo Locating System”, Olin et al., published in 2007) discloses an aircraft cargo locating system that determines the location and weight of aircraft cargo placed in unit loading devices. A wireless tag, such as a Radio Frequency Identification (RFID) tag is affixed to each of the loading devices. The U.S. Pat. No. 7,198,227 system receives information from the tags, and from the information calculates the location of the loading devices and the weight of the loading devices.
U.S. Pat. No. 6,429,810 (“Integrated Air Logistics System”, De Roche, published in 2002) discloses an autonomous cargo tracking system and method comprised of a communication and sensor unit that is affixed to the container to be tracked, a ground system that coordinates communications between the unit and the users, and one or more satellite systems that provide communication capabilities as well as position information.
In systems other than tracking air cargo, barcode scanning is used. For example, US 2010/0230328 (“Intelligent Barcode Systems”, Bonnell et al., published in 2010) discloses systems and methods using intelligent barcodes for processing mail, packages, or other items in transport. It also discloses systems and methods allowing end-to-end visibility of a mail stream by uniquely identifying and tracking mail pieces. In one embodiment of US 2010/0230328, systems and methods using intelligent barcodes allow a mailing service to provide enhanced acceptance, sorting, tracking, address correction, forwarding, and delivery services.
Still in the Art, there are Optical Character Recognition (OCR) methods allowing scanning and processing alphanumeric characters. Such an OCR method is disclosed, for example, in US 2008/0131001 (“Multi-Level Neural Network Based Characters Identification Method and System”, Hofman and Margolin, published in 2008), describing a system and a method, which enable automatic identification of characters while performing and calibrating data verification to ensure data reliability. The system described in US 2008/0131001 can process these identified characters, such as override adverse conditions, adjusting and correcting unclear characters and their images.
US 2008/0063280 (“Character Recognition System and Method”, Hofman and Nikulin, published in 2008) discloses a system and method, which enables precise identification of characters contained in vehicle license plates, container LD, chassis I.D., aircraft serial number and other such identification markings. The system can process these identified characters and operate devices, such as access control operations, traffic systems and vehicle and container tracking and management systems, and provide records of all markings together with their images.
However, presently existing ULD tracking methods require modifications to the unit load devices, such as affixing external modules to the units, for example, RFID tags, or such as changing the standard markings thereof, e.g., by embedding barcode identification in each unit. On the other hand, presently existing character recognition systems are not designed to manage unit load devices.
There is a need in the art, thus, for a mechanism that allows tracking of standard unit load devices.